Doubts cast on cost estimates for high-speed rail alternatives

As the price tag for California's bullet train has soared to nearly $100 billion, a central argument for forging ahead with the controversial project is an even loftier figure: the $171 billion that promoters recently estimated will be needed for new roads and airports if no high-speed rail is built.

Without a fast-rail network, they warn, the state would have to add 2,300 miles of highway and roughly the equivalent of another Los Angeles International Airport to handle a projected surge in future travel.

Now, that alternative is coming under attack by a state-appointed panel of experts, who will soon release an assessment of the rail project's business plan and cast doubt on the accuracy and validity of the $171-billion figure, The Times has learned.